1990-01-09_REVISION - M1988112 (6)

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yp 91 G~ td: l~ $ =P7 9E'S •??47 SPY LEU~~E P. 91 BATTLE MOUhIiAIN RESOURCES, SAN LUIS PROJECT CMLRC ADEQUACY LETTER RESPONSES Page 8 of 28 '4. Please determine and describe the percent moisture content within the tails which would constitute a saturated condition and compare this figure to the anticipated moisture within the desiccated tails. 11111 the amount of water entrained within the tails vary vertically? If so, describe how this would affect the long-term, post reclamation ~stabilr'ty of the facility. RES~UNS~: The results of the laboratory testing of the tailings imiicates that upon consolidation, the tailings will exhibit a void ratio of 0.7 to 0,75. if 100 percent saturated the moisture cont~ant will be app,•oximately 26 to 27.5 percent. !f completely desiccated, the moisture content of the tailings will approach 15 to 20 percent (based on the tailings box depositional modelling, see Appendix E of the amendment). Deposition of the tailings will initially result in a zone of saturated tailinys due to their high rate of rise. These tailings will 6e in contact with the drainage layer and will consolidate and drain. Subsequent deposition will take place using the thin layer deposition technique described in the amendment application (see D.fi.l). Tnis deposition will create beached tailing and will allow '.ha ,;ssiccation to ocr,ur. The desiccation p.ocess will reduce the olsture content of the surface layer to less than saturation. subsequent layers of deposition will wet the top of thee previously desiccated layer, however, the law permeability of the tailings will limit infiltiration of this water, Ps the new layer is desiccated an e?uilibration of the moisture within the two layer will take place. although some incraa;e in the moisture within the lower layer will result, the amount ~f increase is not anticipated to re::atnrdte the pilings. Saturated cor~dittcns will occur bentzth the area of the free water pond during operation. Vertical chan3es in the degree of saturation will, therefore, vary across the impoundment. Some distance upstream of the ?nbankment unsaturated tailinys will extend down to the zone of initial deposition which will itself drain over time. Within tie centre - the facility saturated conditions will occur beneath tt~e pori~i. Under long-term, post reclamation conditions, the moisture cur.: ,~ of the tailings will decrease with time through drainage. Drain~~e will be essentially complete adjacent to the embankment prior to the reclamation of the facility. Orainage of the remairder of the tailings following reclamation will continue, however, equilibrium conditions will result in extremely low drainage sites. The stability of the facility is primarily effected by th~a conditions at and adjacent to the embankment. The tailings 1n this area do nor present concerns as to stability during operations and follnHi~ reclamation, will tend to increase in stability over t•me, v